java - 滚动条不起作用

Question

您好，这是我的滚动条的代码。不幸的是，它不起作用。怎么可能？

text_area = new JTextArea();
text_area.setPreferredSize(new Dimension(250,150));
text_area.setLineWrap(true);
scrollpane = new JScrollPane(text_area); 

当我插入文本并且它比滚动条不出现的区域长时。

这是代码:

public AziendaGUI() {

    company = new Azienda();

    frame = new JFrame("Immobiliari s.p.a");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    view_list = new JButton("View Property");
    view_list.setActionCommand("view_list");
    view_list.addActionListener(this);

    save_list = new JButton("Save List");
    save_list.setActionCommand("save_list");
    save_list.addActionListener(this);

    text_area = new JTextArea();
    text_area.setPreferredSize(new Dimension(250,150));
    text_area.setLineWrap(true);
    scrollpane = new JScrollPane(text_area); //Non funziona la scroll bar

    grid = new GridBagLayout();
    pane = new JPanel(grid);

    /* Set Constraints view_list button */
    grid.setConstraints(view_list, new GridBagConstraints(0,0,1,1,0.0,0.0,GridBagConstraints.WEST,GridBagConstraints.NONE,new Insets(5,5,5,5),0,0));
    pane.add(view_list);

    /* Set Constraints save_list button */
    grid.setConstraints(save_list,new GridBagConstraints(1,0,1,1,0.0,0.0,GridBagConstraints.EAST,GridBagConstraints.NONE,new Insets(5,5,5,5),0,0));
    pane.add(save_list);

    /* Set Constraint text area */
    grid.setConstraints(scrollpane, new GridBagConstraints(0,1,2,1,0.0,0.0,GridBagConstraints.CENTER,GridBagConstraints.NONE,new Insets(5,5,5,5),0,0));
    pane.add(scrollpane);

    frame.setLayout(new FlowLayout());
    frame.add(pane);

    frame.pack();
    frame.setVisible(true);
}

Answer 1

设置 JScrollPane 的首选大小。

请勿不要设置JTextArea的首选大小。

来源:我稍微修改了源代码并且它起作用了。